Method for generating customized ink/media transforms

Abstract

The present invention is directed to an improved system and methodology for generating ink/media transforms. A preferred methodology comprises one or more of the following steps: selecting the ink type; selecting the color set; selecting the media type; selecting the ink saturation level; generating a set of “linearization” color samples, or “ramps”; measuring the linearization ramps; generating a set of “target” color samples, or “patches”; measuring the target patches; screening the target patches and generating the boundary surface of a printer's gamut; implementing an under-color removal (UCR) and black generation (BG); and building the Printer Profile, Transforms and ICC Color Profiles.

1. A method of generating an ink/media transform for a target device, comprising the steps of:
 selecting an ink type; 
 selecting a color set; 
 selecting a media type; 
 selecting an ink saturation level; 
 generating a set of linearization ramps; 
 measuring the linearization ramps; 
 generating a set of target patches, wherein each generated patch has corresponding Lab values; 
 measuring the target patches; 
 screening the measured target patches and generating a boundary surface of a gamut for the target device, wherein the step of screening each target patch comprises the steps of:
 accepting a patch having a threshold maximum lightness value (L) value for a preselected ink coverage value and discarding patches having an ink coverage value that is higher than the threshold maximum lightness value (L); 
 
 implementing under-color removal and black generation; and 
 building the transform. 
 
   
   
     2. The method as claimed in  claim 1 , including the step of:
 converting the Lab values for each patch to CIEXYZ values, and subsequently resetting them to back to CIELab values. 
 
   
   
     3. The method as claimed in  claim 1 , including the step of eliminating patches that contain an ink coverage amount that is inconsistent with a specified hue value. 
   
   
     4. The method as claimed in  claim 3 , including the steps of:
 (a) identifying and discarding patches that satisfy criterions of both containing 100% of a non-primary color and containing less than 100% of a non-primary ink that comprises the color; 
 (b) identifying and discarding patches tat satisfy criterions of both containing 75% of the non-primary color and containing less than 75% of the non-primary ink that comprises the color; and 
 repeating steps (a) and (b) for all non-primary color ink levels of the color set. 
 
   
   
     5. The method as claimed in  claim 1 , including the steps of:
 (a) identifying and discarding patches that satisfy criterions of both containing 100% of a non-primary color and containing less than 100% of a non-primary ink that comprises the color; 
 (b) identifying and discarding patches that satisfy criterions of both containing 75% of the non-primary color and containing less than 75% of the non-primary ink that comprises the color; and 
 repeating steps (a) and (b) for all non-primary color ink levels of the color set. 
 
   
   
     6. The method as claimed in  claim 5  including the steps of:
 eliminating patches with color values that include pure black ink. 
 
   
   
     7. The method as claimed in  claim 1 , wherein the step of screening each generated target patch comprises the steps of:
 accepting a patch having at least a threshold chroma value for a preselected ink coverage value and discarding patches having an ink coverage value that is higher than the threshold chroma value. 
 
   
   
     8. A method of generating an ink/media transform for a target device in which an ink type, a color set media type and an ink saturation level have all been selected, a set of linearization ramps have been generated and measured, and a set of target patches have been generated and measured, the method comprising the steps of:
 screening the set of target patches, wherein each generated patch has corresponding Lab values, wherein the step of screening each generated target patch comprises the steps of:
 (a) accepting a patch having a threshold maximum lightness value (L) value for a preselected ink coverage value and discarding patches having an ink coverage value that is higher than the threshold maximum lightness value (L); 
 (b) accepting a patch having at least a threshold maximum chroma value for a preselected ink coverage value and discarding patches having an ink coverage value that is higher than the threshold maximum chroma value; 
 (c) eliminating patches that contain an ink coverage amount that is inconsistent with a specified hue value; 
 (d) identifying and discarding patches that satisfy criterions of both containing 100% of a non-primary color and containing less than 100% of a non-primary ink that comprises the color; 
 (e) identifying and discarding patches that satisfy criterions of both containing 75% of the non-primary color and containing less than 75% of the non-primary ink that comprises the color; and 
 (f) repeating steps (d) and (e) for all non-primary color ink levels of the color set; 
 (g) eliminating patches with color values that include pure black ink; 
 
 determining in-gamut and out-of-gamut colors for the transform by using a 3-dimensional Delauney Tessellation, wherein each vertice corresponds to a coordinate point position of a target patch, and a final gamut boundary re-shaping method used in a profile building process; 
 performing 3-dimensional interpolation from nearby vertices when transforming color values for colors that are not directly represented in the LUT data set; and 
 building the transform includes the steps of:
 constructing a hypercube of dimensions 15×15×15 uniformly spaced points in a CIELab color space; 
 creating a look-up table containing a transformation value for each of the selected color patch values by indexing the corresponding Lab values to corresponding coordinates in the color space; 
 implementing a baricentric interpolation and gamut-mapping procedure to fill out the transform LUT with a complete set of values. 
 
 
   
   
     9. The method as claimed in  claim 8 , including the step of extending the 15×15×15 hypercube to a 100×100×100 hypercube to create a transform file by using a tri-linear interpolation wherein a color point is found from vertices of a tetrahedron that fall within a color space tessellation. 
   
   
     10. The method as claimed in  claim 9 , including the step of interpolating the ink values from the tessellation by using a gamut-mapping algorithm for Lab points outside the tessellation, in which a gamut-mapping algorithm attempts to locate a position on the gamut edge that is at a same hue angle and provides a desired result. 
   
   
     11. A method of generating an ink/media transform for a target device, comprising the stops of:
 selecting an ink type; 
 selecting a color set; 
 selecting a media type; 
 selecting an ink saturation level; 
 generating a set of linearization ramps; 
 measuring the linearization ramps; 
 generating a set of target patches; 
 measuring the target patches; 
 screening the measured target patches and generating a boundary surface of a gamut for the target device, wherein the step of screening each generated target patch comprises the steps of accepting a patch having at least a threshold maximum chroma value for a preselected ink coverage value and discarding patches having an ink coverage value that is higher than the threshold maximum chroma value; 
 implementing under-color removal and black generation; and 
 building the transform. 
 
   
   
     12. The method as claimed in  claim 11 , including the step of eliminating patches that contain an ink coverage amount that is inconsistent with a specified hue value. 
   
   
     13. The method as claimed in  claim 11 , including the steps of:
 (a) identifying and discarding patches tat satisfy criterions of both containing 100% of a non-primary color and containing less than 100% of a non-primary ink that comprises the color; 
 (b) identifying and discarding patches that satisfy criterions of both containing 75% of the non-primary color and containing less than 75% of the non-primary ink that comprises the color; and 
 repeating steps (a) and (b) for all non-primary color ink levels of the color set. 
 
   
   
     14. A method of generating an ink/media transform for a target device, comprising the steps of:
 selecting an ink type; 
 selecting a color set; 
 selecting a media type; 
 selecting an ink saturation level; 
 generating a set of linearization ramps; 
 measuring the linearization ramps; 
 generating a set of target patches; 
 measuring the target patches; 
 screening the target patches and generating a boundary surface of a gamut for the target device, and determining in-gamut and out-of-gamut colors for the transform by using a 3-dimensional Delauney Tessellation, wherein each vertice corresponds to a coordinate point position of a target patch; 
 implementing under-color removal and black generation; and 
 building the transform. 
 
   
   
     15. The method as claimed in  claim 14 , including the step of performing 3-dimensional interpolation from nearby vertices when transforming color values for colors that are not directly represented in a LUT data set. 
   
   
     16. A method of generating an ink/media transform for a target device, comprising the steps of:
 selecting an ink type; 
 selecting a color set; 
 selecting a media type; 
 selecting an ink saturation level; 
 generating a set of linearization ramps; 
 measuring the linearization ramps; 
 generating a set of target patches, wherein each generated patch has corresponding Lab values; 
 measuring the target patches; 
 screening the target patches and generating a boundary surface of a gamut for the target device; 
 implementing under-color removal and black generation; and 
 building the transform, including the steps of:
 constructing a hypercube of dimensions 15×15×15 uniformly spaced points in the CIELab color space; 
 creating a look-up table containing a transformation value for each of the selected color patch values by indexing the corresponding Lab values to corresponding coordinates in the color space; and 
 implementing a baricentric interpolation and gamut-mapping procedure to fill out the transform LUT with a complete set of values. 
 
 
   
   
     17. The method as claimed in  claim 16 , including the step of:
 extending the 15×15×15 hypercube to a 100×100×100 hypercube to create a transform file using a tri-linear interpolation wherein a color point is found from vertices of a tetrahedron that fall within a color space tessellation. 
 
   
   
     18. The method as claimed in  claim 17 , including the steps of providing correspondence between an ICC profile and a custom transform by creating a cube the size of the ICC cube and then scaling it up linearly. 
   
   
     19. The method as claimed in  claim 18 , including the step of interpolating the ink values from the color space tessellation by using a gamut-mapping algorithm for Lab points outside the tessellation, in which the gamut-mapping algorithm attempts to locate a position on the gamut edge that is at a same hue angle and provides a desired result. 
   
   
     20. The method as claimed in  claim 17 , including the steps of providing correspondence between an ICC profile and a custom transform by creating a cube the size of the ICC cube and then scaling it up linearly.